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Grapefruit Juice and Medicines

Topic Overview

How does grapefruit juice affect medicines?

Grapefruit juice contains chemicals that can cause problems with
enzymes that break down certain types of medicines in
your intestines. When a medicine does not get broken down properly in the
intestines, you can have too much medicine in your blood. Having too much medicine in your blood
increases your chances of having side effects.

Which medicines are affected by grapefruit juice?

Most medicines are not affected by grapefruit juice.
And not all medicines for the health problems listed below are
affected by grapefruit juice. But more than 50 medicines
are affected by grapefruit juice. These
can include medicines for:

Abnormal heart
rhythm.

Allergies.

Anxiety.

Asthma.

Blood
clots.

Cancer.

Cough.

Depression.

Emphysema.

Epilepsy.

Erectile dysfunction.

Heart attack or heart
disease.

High blood pressure.

High
cholesterol.

HIV.

Infection.

Pain.

Enlarged prostate.

Stroke.

Is grapefruit juice safe for you?

If you regularly drink grapefruit juice, ask your doctor or pharmacist if any
of your medicines are affected by grapefruit juice. If your medicine is making
you feel sick or is causing unusual or uncomfortable side effects, talk to your
doctor.

All new medicines are tested for problems caused by
grapefruit juice before they are approved by the Food and Drug Administration
(FDA). Medicines that are affected by grapefruit juice must have warnings in
their patient information sheets. When you pick up a new medicine, your
pharmacist will talk to you or give you written information about foods to
avoid while taking your medicine. Some medicines may also have warnings on the
"food-drug interactions" section of the bottle label.

In general,
the more grapefruit juice you have, the greater the possible effects.1 It has been shown that even one glass of grapefruit juice—at
any time of the day—is enough to cause certain medicines to work differently
than they are supposed to.2 Sometimes the effects of
one glass of juice can last up to 3 days.

In many cases, you may
be able to have a glass of grapefruit juice without problems. Ask your doctor
or pharmacist how much is safe for you.

What can happen if grapefruit juice affects your medicine?

The problems you may have
from taking medicines that are affected by grapefruit juice depend on the kind
of medicine you are taking and how your body reacts. Some
problems are mild, while others are more serious. In general, older people are
more likely than younger people to have serious problems.

For example,
if you are taking a medicine for high blood pressure, you may develop
dangerously low blood pressure. If you are taking a medicine for high
cholesterol, you may develop increased side
effects.

For more specific information on the kinds of
health problems you could have if you drink grapefruit juice while taking a
certain medicine, talk to your doctor or pharmacist.

How can you prevent problems?

You can take steps to
avoid problems with grapefruit juice and your medicine.

Before you take any medicine, ask your doctor
or pharmacist if you can safely drink grapefruit juice.

Read the
labels on foods and natural health products to make sure they do not contain
grapefruit, grapefruit juice, or grapefruit extract. Seville oranges (which are sometimes used in marmalade but not in orange
juice), pomelos, and tangelos may also
cause problems.3

Always read the
warning labels for any medicine you are taking. If you have questions, ask your
doctor or pharmacist.

Tell your doctor if you are having unusual or
uncomfortable side effects from your medicine.

Tell your doctor and other health professionals about all the
medicines you are taking. This includes herbs, vitamins, homeopathic products, supplements, and over-the-counter medicines.

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